Key points are not available for this paper at this time.
Relative carbon isotope ratio (delta13C values) of primary and secondary products from different compartments of annual plants, pine needles, wood, and decomposing Basidiomycetes have been determined. An enrichment in 13C was found for storage tissues of annual plants, because of the high level of the primary storage products sucrose and starch; however, the enrichment was even greater in leaf starch. All of these compounds had the same relative 13C enrichment in positions 3 and 4 of glucose. Secondary products in conifer needles (lignin, lipids) were depleted in 13C by 1 to 2 per mille (thousand) sign relative to carbohydrates from the same origin. Air pollution caused a small decrease in delta13C values; however, the relative content of plant products, especially of the soluble polar compounds, was also affected. Decomposing fungi showed a global accumulation of 13C by 4per mille (thousand) sign relative to their substrates in wood. Their chitin was enriched by 2per mille (thousand) sign relative to the cellulose of the wood. Hence, Basidiomycetes preferentially metabolize "light" molecules, whereas "heavy" molecules are preferentially polymerized. Our results are discussed on the basis of a kinetic isotope effect on the fructose-1,6-bisphosphate aldolase reaction and of metabolic branching on the level of the triose phosphates with varying substrate fluxes.
Gleixner et al. (Sun,) studied this question.